Question: Who did Buster Keaton marry on May 31, 1921?
Paraphrase: On May 31, 1921, who wed Buster Keaton?
SPARQL (Wikidata): SELECT ?obj WHERE { wd:Q103949 p:P26 ?s . ?s ps:P26 ?obj . ?s pq:P580 ?x filter(contains(YEAR(?x),'1921')) }